With respect to wireless communications, the basic underlying physical resource is radio spectrum. Although small spans of additional radio spectrum have become available for wireless communication systems, such as Wireless Wide Area Networks (WWANs), ultimately radio spectrum is a limited resource. Efficient use of the available radio spectrum, therefore, is one key to dealing with the continually increasing demands placed on WWANs.
Increasing spectral efficiency within the context of WWANs can involve special considerations. For example, the mobile radio channels associated with WWANs can be highly time-variant and dispersive. The time varying and dispersive nature of such channels can be addressed in part by multicarrier modulation. Multicarrier modulation can be inefficient due to the application of guard bands between carriers to avoid Inter-Carrier Interference (ICI).
Currently, gains are being made with respect to spectral efficiency in WWANs through the use of Orthogonal Frequency Division Multiplexing (OFDM). By setting the various subcarriers of a multi-carrier WWAN at harmonic frequencies, they can be made orthogonal one to another. As a result, guard bands between sub-carriers can be omitted and sub carriers can even overlap with respect to frequency. Implementation of OFDM in WWANs, such as those consistent with the Third Generation Partnership Project (3GPP) Long Term Evolution (LTE) standards, has allowed important gains to be made with respect to spectral efficiency. However, important gains remain to be made with respect to spectral efficiency not only by means of additional technologies, but by improving the spectral efficiency of OFDM implementations themselves.
Reference will now be made to the exemplary embodiments illustrated, and specific language will be used herein to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended.